1. Field of the Invention
This invention relates to inflatable bags for use in airbag passive restraint systems that are mounted forwardly of driver's seats of vehicles and adapted to be inflated automatically and instantaneously in case of a collision accident of the vehicle, thereby to restrain movement of the seated occupant and to protect the occupant, and to a method of manufacturing them. More particularly, the invention is directed to inflatable bags which are regulated in the directions of deployment and improved in the deployed configuration when inflated, and their manufacture.
2. Description of Related Art
Air bag passive restraint systems for vehicles are to restrain movement of a passenger or seated occupant and to protect the person by instantaneous inflation of the bag and its shock-absorbing ability in case of collision of the vehicle at an impact of more than a predetermined magnitude, thus acting as an auxiliary to seat belts. Generally, an air bag passive restraint systems is made up of an inflator for releasing gas, e.g. nitrogen, a bag to be inflated by the gas released, a housing enclosing therein air-tightly the inflator and bag, and a sensor detecting an impact of more than a predetermined magnitude and transmitting a signal to the inflator. A typical inflatable bag comprises two upper and lower base cloths of the same circular form seamed together at the outer peripheries, the lower base cloth having an opening through which to communicate with the inflator. An improved bag is also known, which is further provided with strip pieces for regulating excessive upward flaring of the bag, which pieces extend from an inner periphery of the lower cloth to the upper cloth, thereby avoiding hitting of the occupant on the head and thorax by the flared bag itself.
When the air bag passive restraint is brought into operation, the gas released from the inflator is filled into the bag and housing to exert an inner pressure upon the wall face of the bag, which urges to inflate and fully deploy the bag.
With known air bag passive restraint systems for driver, the inflator is embedded in the central part of a steering wheel and the inflatable bag is, upon operation, inflated to flare in a mushroom form over the circumference of the steering wheel thereby to protect the occupant in such a manner that the inflated bag is interposed between the steering wheel and the occupant. With the aforesaid airbag passive restraints for driver, their inflatable bags, mostly comprising two- or multi- compartment type bags, were deployed over the steering wheel, but not in a manner wrapping successfully the outer circumference of the steering wheel therein.
On the other hand, a conventional method for manufacturing the aforesaid existing bag necessitated a multiplicity of parts such as the strip pieces and accordingly, required laborious sewing work of them to many seaming places. As a result, the method required much time and skill and was not efficient.
In view of the problems above, it is a primary object of this invention to provide air bag passive restraint systems for driver, particularly inflatable bags thereof improved in the deployed configuration which bags are formed of a single bag (with no compartment) and can be deployed in a manner enveloping satisfactorily the steering wheel therein.
It is another object of this invention to provide a method of manufacturing inflatable bags for air bag passive restraints, which method enables a simple and efficient procedure.